Hi All;
> I have think about it. I concern about Real Mode Interrupt. Since JJOS is
>running under Protected Mode.
> As I know, most of the real mode interrupt will not work under protected mode. If
>JJOS can provide a Real
> Mode Interface, we could save lots of times.
I thought about this when I was working on early versions of jjos. There is an
analogous software suite for DOS called "Dos Protected Mode Interface" (a.k.a.,
DPMI). It is a sort of DOS-extender which enables calls to real-mode DOS (and
hence BIOS) calls from protected-mode code -- sort of what you're asking for
here. This was especially attractive when I thought it was unavoidable to write
my own boot loader (just use BIOS calls to do it all).
However, the more I looked into it, the messier it got. The DPMI implementation
I was looking at basically had to reimplement, for every "interesting" real-mode
DOS/BIOS call, a protected-mode interface. It seemed to include marshalling and
unmarshalling args/params/return-values on a case-by-case basis, etc., and
implementing the mechanics of the task switch. Interrupt-handling also got
weird. It was not clear how it would work in a multi-threaded way (although I
might've overlooked that capability entirely). It was a *big* effort. However,
if you want to run under DOS (say, a game), but you also want a 32-bit flat
address space, it's the only way to go.
For us, that would be an awful lot of work (it would've taken me a year
part-time), and we really want to do the device handling in Java anyways, so it
didn't seem like a good idea at the time. Plus, it wouldn't really even be
close to being a portable approach...
On the other hand, there *is* the virtual 8086 mode, which is supposed to help
do stuff like this (even though it's utterly non-portable).
-jm
--
==== John Morrison ==== MaK Technologies, Inc.
==== Chief Technology Officer ==== 185 Alewife Brook Pkwy, Cambridge, MA 02138
==== [EMAIL PROTECTED] ==== http://www.mak.com/
==== vox:617-876-8085 x115 ==== fax:617-876-9208
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